1. Field of the Invention
The apparatus and process of the present invention relates to connecting a specific heating tube to a surrounding external sleeve. More particularly, the present invention relates to an improved design method for providing a seal tight connection between an air preheater tube and an external sleeve surrounding the tube.
2. General Background of the Invention
In the design of an air preheater tube utilized in heat exchange systems, there is normally provided an APH (air preheater tube) which is positioned within an external sleeve, there being a sealing engagement between the tube and the external sleeve. In order to increase the strength of the connection between the tube and the external sleeve, yet maintain its flexibility and resistance to thermal shock, it is necessary that there be provided a specific gap of less than 0.005 inches between the tube and the external sleeve. One of the problems confronted in this particular type of a process of forming such a seal, is the fact that if the tube is expanded to seal against the inner surface of the surrounding sleeve, then there may result in a less than smooth-straight inner surface of the tube. Therefore, when heated gases carrying particles travel through the tube opening, the result may be the build up of carbon or the like material within the recesses or non-straight portions of the tube which are not conducive to efficient operation of the heat exchange system. Therefore, there is a need in the art for a system and apparatus whereby the tube and the surrounding sleeve may be formed in such a manner as to provide a less than 0.005 inch gap between the surface of the tube and the surface of the surrounding sleeve, yet while maintaining the inner surface of the tube smooth and straight so as to avoid any particle build up on the inner surface of the tube.
In a patentability search conduced on this apparatus and process, there have been cited several patents which may be pertinent to this invention, and these are being submitted herewith in the prior art statement filed.